Production of aviation gasoline



United States Patent cc 7 2,944,003 Patented July 5, 1960 PRODUCTION orAVIATION GASOIJNE Wilhelmns M. J. 'Ruedisulj, The Hague, and Marius ftHart, Amsterdam, Netherlands, asignors to Shell Oil Company, acorporation .of Delaware No Drawing. Filed on. 27', 1955, Ser. No.543,271

Claims priority, application Netherlands Oct. 29, 1954 4 Claims. (cl.208-93) This invention relates to the production of 100/130 gradeaviation gasoline and to the aviation gasoline so produced.

An object of the invention is to provide a process for the production of100/ 130 grade aviation gasoline which meets the specifications for such(MIL-F-5572A) and is less costly than when produced by previous methodsinvolving reformed aviation base stocks.

Another object of the invention is to provide a novel aviation gasolinecomposition which meets the specifications for 100/130 grade and may beproduced in larger quantities per given volume of alkylate.

The process of the invention broadly consists in the blending of certainknown aviation gasoline constituents in new proportions with an aviationbase stock prepared from a selected straight-run gasoline fractionthrough fractionation, platforming, reblending, and stabilization. Theaviation gasoline broadly consist essentially of the specially preparedbase stock in an amount upward of 30% by volume, alkylate in asubstantial amount less than 50% by volume, minor amounts of isopentaneor isopentane plus butane sufiicient to satisfy the vapor pressure andvolatility requirements, ethyl fluid and dye in an amount within thespecification limits, and the remainder, if any, consisting of a heavyplatformate fraction.

It is known that the octane number of straight-run gasolines andfractions thereof can be increased to an especially high degree in apractical operation by platforming them by which is understood atreatment thereof in the presence of added hydrogen and under suitabledehydrogenation conditions of temperature and pressure with an acidicplatinum catalyst, The acidic platinum catalyst consists essentially offrom 0.1 to 1% of platinum combined with an acidic support such as analumina acidified by the inclusion of combined chlorine and/ or fluorineor a cracking catalyst such as the proprietory silica-alumina,silica-magnesia, silica-zirconia, alumina-boria, etc., crackingcatalysts. The particular advantage of platforming over the olderso-called hydroforming with catalysts promoted with such materials asthe oxides of molybdenum, chromium, cobalt, nickel, and tungsten, isthat in the platforming process a definite and controlled amount ofselective hydrocracking is effected and isomerization reactions arecatalyzed to a much greater degree. The platforming operation isnormally carried out under dehydrogenation conditions at temperaturesbetween about 450 C. and 550 C. and under pressures between about 2 and100 atmospheres.

Through the use of platforming as described, straightrun gasoline can beimproved and improved in practical operation to an extent allowing useof the product as a component in premium grade motor gasoline. However,it has been determined that the components of straightrun gasolineboiling below about 85-95 C. are not materially improved by suchtreatment and it is the usual practice therefore to separate from thefeed to the platforming operation the light components, i.e., thoseboil- 2 ing up to -95 C. and only platform the heavier part after whichthe light components which usually already have a fairly high octanenumber are combined with the platformate.

The products thus obtained, even when starting with a naphthem'cgasoline, cannot however, not withstanding their high octane numbergenerally be used as a component in the preparation of /130 gradeaviation gasoline since when the said products are blended with theusual aviation gasoline components such as alkylate prepared fromisobutane and butenes and/or pentenes, and isopentane, it is usuallyimpossible to prepare mixtures which satisfy all the special and verystrict requirements which are today made of such aviation gasoline,especially with respect to the volatility, heating value, stability andperformance number (which is a measure of the take-oft load) with themaximum lead content which is permissible according to thespecifications.

It is, however, sometimes possible to prepare such mixtures when theplatformate is derived from a naphthenic gasoline fraction boilingbetween approximately 8S-95 C. and -140 (3., provided the content of thesaid component in the mixture is kept to a relatively low value belowabout 30% by volume which means that the mixture has a high alkylatecontent, viz. more than 50% by volume. This limitation with respect tothe content of the platformate is, however, a drawback since thiscomponent is not only considerably cheaper than alkylate but is alsomore readily prepared starting with initial materials which are muchmore available.

The invention now provides a process whereby 100/130 grade aviationgasoline may be prepared with platformate and with lesser quantities ofalkylate thereby afiording a lower cost per gallon of gasoline and alarger aviation gasoline production per given amount of alkylate.

The process according to the invention comprises separating a fractionboiling between approximately 65 C. and approximately l30-l40 C. from anaphthenic straight-run gasoline, platforming this fraction undersuitable conditions, combining the platformate so obtained with thefraction boiling up to approximately 65 C. of the starting gasoline orwith -a part thereof, stabilizing the resultant mixture, and blendingtherewith the required amounts of alkylate, isopentane and/or butane,ethyl fluid and in some cases a small amount of heavy platformate. It isessential that a highly naphthenic straightrun gasoline containingupward of about 40% by weight of naphthenes be used as the startingmaterial. Less naphthenic gasolincs and especially natural gasoliues areunsuited.

The platformate obtained as described has a higher octane number andperformance number than those in which a gasoline fraction boilingbetween 85-95 and 130-140" C. derived from the same starting gasoline isused, but which is otherwise obtained in the same way, and can be mixedin quantities upward of 30% with the usual aviation gasoline componentssuch as alkylate in an amount less than 50% and isopentane to formproducts which satisfy every requirement made of the aviation gasoline.

It is surprising that by increasing the boilingrange of the straight-runmaterial platformed to include that part which has hitherto beenconsidered best emitted a greater proportion of the platformed basestock can be used with a reduced requirement for alkylate.

The platforming treatment is carried out in a manner known per se;however, under a narrower range of conditions viz. a pressure lower than50 atmospheres preferably 2-30 atmospheres since with higher pressures,particularly when operating at temperatures higher than 5 00 C., theyield of liquid product is lower and moreover the quality of the productas a aviation gasoline component declines. Temperatures lying betweenapproximately 450 and 525 C. are used.

After. separating the hydrogen gas phase which is produced in theplatforming operation and which isrecycled in the process, the liquidplaformate obtained is combined with the components separated from thestarting gasoline and boiling up to approximately 65 C. or with a partthereof. The pentane and lighter hydrocarbons in the mixture are thenremoved by stabilization. This is effected in a stabilization column inthe manner used for stabilizing motor gasolines. The stabilized productthus obtained which is withdrawn from the bottom of the stabilizer formsthe desired component from which by mixing with alkylate, isopentane,ethyl fluid, dye, and small amounts of any additional components,aviation gasoline of the required specification is prepared at a lowercost and greater yield per gallon of available alkylate.

It has been found to be also advantageous to use the above mentionedplatformate product together with a low amount (in relation to thisproduct) of the fraction of this product boiling above approximately 105C. as a component in the aviation gasoline since by also using he saidheavy fraction in a small quantity, which in connection with thevolatility requirement of aviation gasoline should not generally exceedabout 20% of the volume of the platformate product, it is possible tomake a considerably further reduction in the content of alkylate in theaviation gasoline, e.g., to below 40%.

Example .1

Starting from a Venezuelan gasoline having a naphthene content of 52% byweight and a final boiling point of 150 C. a fraction boiling between 65C. and 135 C. was separated by fractional distillation in a quantity of73.7% by weight. This fraction was platformed with commercialplatforming catalyst at a through-put rate of 2.1 liters per liter ofcatalyst per hour together with hydrogen of 96% purity derived from theprocess in a quantity corresponding to 4.8 mols of hydrogen per mol ofthe gasoline fraction at approximately 490 C. and a pressure ofapproximately 30 atmospheres.

After separating the hydrogen-rich gas phase which was recycled, theliquid platformate which was obtained in a yield of 95% by weight,calculated on the gasoline fraction introduced, was combined with thecomponents boiling below 65 C. which had been previously separated fromthe starting gasoline in a quantity of 17.3% by weight. The mixture wasthen freed in a stabilizing column of the pentane and lighterhydrocarbons still dissolved therein. The' stabilized bottoms productwithdrawn from the stabilizing column was obtained in a yield of 75.8%by weight based on the gasoline.

This product was combined with an alkylate prepared from isobutane and amixture of butenes and pentenes and with isopentane and butane to form amixture of the following composition in percentages by volume:

The mixture thus obtained had, after addition of 4 m1. of tetraethyllead per US. gallon an F-4 performance number of 132.6 and in respect ofall other properties satisfied the specification for aviation gasolineof 100/ 130 grade.

For the purpose of comparison it may be stated that when in separatingthe gasoline fraction to be reformed from the starting material thelower cutting temperature chosen was 85 C. instead of 65 C., otheroperating conditions remaining the same, a stabilized bottom prodnot wasobtained with which no mixture satisfying the specifications for 100/130 grade aviation gasoline could be prepared with theother componentreferred to above unless the content of stabilized bottom product wasreduced to 27.5% by volume and the alkylate content was increased to 54%by volume.

This shows therefore that by operating according to the invention aconsiderable saving of alkylate can be effected.

Example II Stabilized product 40.5 Heavy platformate fraction 6.0Alkylate 38.2 lsopentane 12.3 Butane 3.0

After addition of 4 ml. of TEL per US. gallon this mixture had an F-4performance number of 132.6 and in respect of all other properties itsatisfied the specification for aviation gasoline of 100/130 grade.

vA comparison of the composition of this mixture with that of theaviation gasoline referred to in Example I shows that the alkylatecontent of the final mixture can be reduced further by also adding asmall percentage of the heavy platformate fraction.

We claim as our invention: a

1. Aviation gasoline meeting the specification for 100/ 130 grade whichconsists essentially of alkylate in a substantial amount but less thanby volume, a minor amount of isopentane suflicient'to meet thevolatility requirements, tetraethyl lead in permissible amounts, and adepentanized catalytic reformate/straight-run stock obtained by (1)catalytically reforming a fraction of a straight-run gasoline containingat least 40% by Weight naphthenes, said fraction having a lower cuttingpoint of about C. and an upper cutting point of about l30-l40 C., bycontacting it with an acidic platinum catalyst at a pressure between 2and 30 atmospheres and a temperature between 450 and 525 C., (2)blending with the catalytic reformate the lower boiling material boilingup to about 65 C. separated from the said straight-run gasoline and(3)'depentanizing the catalytic reformate/straight-run blend, said stockcomprising at least 30% by volume of the gasoline, and any additionalcomponents in the gasoline being present in an amount less than 20% byvolume of said stock.

2. An aviation gasoline according to claim 1 further characterized incontaining a minor amount, less than 20% by volume of the depentanizedcatalytic reformate/ raight-run stock, of a heavy reformate fractionprepared by removing from a portion of the catalytic reformate thematerial boiling up to about C.

3. Process for the production of 100/ grade aviation gasoline whichcomprises (1) separating from a naphthenic straight-run gasolinecontaining at least 40% by weight naphthenes by fractional distillationa light ends fraction boiling up to about 65 C. anda fraction having alower cutting point of about 65 C. and an upper cutting point of about130-140 C., (2) catalytical- 1y reforming the latter fraction bycontacting it with an acidic platinum catalyst under a pressure between2 and 30 atmospheres at a temperature between 450 and 525 C., (3)blending the catalytic reformate thus obtained with the said light endsfraction from the straightr'un gasoline, '(4) stabilizingthe catalyticreformate/ straight'run blend, and (5) blending the stabilized productthus obtained in an amount at least 30% by volume of the finishedaviation gasoline with less than 50% by volume Of lky ate; a minoramount of isopentane sufli- 1 l l l cient to meet the volatilityrequirements and tetraethyl lead in permissible amounts, any additionalcomponents being present in an amount less than 20% by volume of thesaid stabilized product.

4. Process for the production of 100/130 grade aviation gasoline whichcomprises (1) separating from a naphthenic straight-run gasolinecontaining at least 40% by weight naphthenes by fractional distillationa light ends fraction boiling up to about 65 C. and a fraction having alower cutting point of about 65 C. and an upper cutting point of about130-140 C., (2) catalytically reforming the latter fraction bycontacting it with an acidic platinum catalyst under a pressure between2 and 30 atmospheres at a temperature between 450 and 525 C., (3)fiactionating a part of the catalytic reformate thus obtained toseparate a heavy fraction boiling above about 105 C., (4) blending theremainder of said catalytic reformate with at least part of said lightends fraction, (5) stabilizing the catalytic reformate/ straight-runblend, (6) blending the stabilized product thus obtained in an amount atleast 30% by volume of the finished gasoline with less than 20% byvolume,

based on the stabilized product, of said heavy catalytic reformate,alkylate in an amount less than by volume based on the gasoline, a minoramount of isopentane sufiicient to meet the volatility requirements andtetraethyl lead in permissible amounts.

References Cited in the file of this patent UNITED STATES PATENTS2,311,498 Voorhies Feb. 16, 1943 2,593,561 Herbst et al Apr. 22, 19522,626,893 Morrow Jan. 27, 1953 2,684,325 Deanesly July 20, 19542,698,829 Haensel Jan. 4, 1955 2,736,684 Tarnpoll Feb. 28, 19562,740,751 Haensel et al. Apr. 3, 1956 2,792,336 Kubicek et al. May 14,1957 2,874,114 Ruedisulj Feb. 17, 1959 OTHER REFERENCES Oil and GasJournal, vol. 49, No. 45, March 15, 1951, pp. 68, 69, 71, 72, 75, 76, 77(article by Read, Aviation Fuels).

3. PROCESS FOR THE PRODUCTION OF 100/130 GRADE AVIATION GASOLINE WHICHCOMPRISES (1) SEPARATING FROM A NAPHTHENIC STRAIGHT-RUN GASOLINECONTAINING AT LEAST 40% BY WEIGHT NAPHTHENES BY FRACTIONAL DISTILLATIONA LIGHT ENDS FRACTION BOILING UP TO ABOUT 65*C. AND A FRACTION HAVING ALOWER CUTTING POINT OF ABOUT 65*C AND AN UPPER CUTTING POINT OF ABOUT130-140*C., (2) CATALYTICALLY REFORMING THE LATTER FRACTION BYCONTACTING IT WITH AN ACIDIC PLATINUM CATALYST UNDER A PRESSURE BETWEEN2 AND 30 ATMOSPHERES AT A TEMPERATURE BETWEEN 450 AND 525*C., (3)BLENDING THE CATALYTIC REFORMATE THUS OBTAINED WITH THE SAID LIGHT ENDSFRACTION FROM THE STRAIGHTRUN GASOLINE, (4) STABILIZING THE CATALYICREFORMATE/ STRAIGHT-RUN BLEND, AND (5) BLENDING THE STABILIZED PRODUCTTHUS OBTAINED IN A AMOUNT AT LEAST 30% BY VOLUME OF THE FINISHEDAVIATION GASOLINE WITH LESS THAN 50% BY VOLUME OF ALKYLATE, A MINORAMOUNT OF ISOPENTANE SUFFICIENT TO MEET THE VOLATILITY REQUIREMENTS ANDTETRAECTHYL LEAD IN PREMISSIBLE AMOUNTS, ANY ADDITIONAL COMPONENTS BEINGPRESENT IN AN AMOUNT LESS THAN 20% BY VOLUME OF THE SAID STABILIZEDPRODUCT.